The present invention generally relates to light beam heating apparatuses which enable local heating by converging light from a light source such as a light emitting lamp, a laser diode or the like. More particularly, it relates to a light beam heating apparatus suitable for heating in soldering, removal of a coating of a small-diameter polyurethane wire, heating of synthetic resin, etc.
Light beam heating apparatuses in which light from a light source such as a light emitting lamp, a laser diode or the like is incident upon one end of an optical fiber, and light emitted from the other end of the optical fiber is reconverged by using a lens mechanism so as to heat an article disposed in the vicinity of a point of convergence are widely used in recent years as non-contact local heating apparatuses for soldering electronic components, heating or fusing synthetic resin, etc.
Hereinafter, a construction of the known light beam heating apparatuses and heating of the article by the known light beam heating apparatuses are described with reference to FIGS. 9 and 10. FIGS. 9 and 10 show a construction of a conventional light beam heating apparatus and soldering of an article by the conventional light beam heating apparatus. The conventional light beam heating apparatus includes a light emitting lamp 1 (for example, a xenon lamp) for emitting light 3, an elliptical reflector 2 and an optical fiber 4. The optical fiber 4 has a light receiving end 4a for receiving light converged by the elliptical reflector 2 and an output end 4b such that the light incident upon the light receiving end 4a is outputted as light 5 from the output end 4b. The conventional light beam heating apparatus further includes a lens mechanism 6 which reconverges the light 5 outputted from the output end 4b of the optical fiber 4 into light 7. In order to cause the light 7 to have a focal diameter 8 required for an article 9 to be heated, the lens mechanism 6 has an adjustment stroke 10 relative to the output end 4b of the optical fiber 4.
In this conventional light beam heating apparatus, the light 3 emitted from the light emitting lamp 1 is converged by the elliptical reflector 2. The light receiving (input) end 4a of the optical fiber 4 is provided at the point of convergence such that the light is incident upon the light receiving end 4a. In order to cause the light 7 to have the focal diameter 8 required for the article 9, the lens mechanism 6 and the output end 4b of the optical fiber 4 are fixed at the adjustment stroke 10 such that the light 5 outputted from the output end 4b of the optical fiber 4 is reconverged into the light 7 by using the lens mechanism 6. A focal point of this reconverged light 7 is made coincident with the article 9 such that the article 9 is heated by the light 7.
However, in the conventional light beam heating apparatus referred to above, it is difficult to arbitrarily change the focal diameter 8 of the light 7 having passed through the lens mechanism 6. Therefore, in case a plurality of articles having different diameters are to be heated, a plurality of light beam heating apparatuses should be provided for different focal diameters thereby resulting in a huge investment. Alternatively, if a single light beam heating apparatus is adjusted to a minimum focal diameter for one of the articles and the remaining articles are also heated by the light beam heating apparatus, the remaining articles are heated at the improper focal diameter. Therefore, tact time is increased, thus resulting in inefficient heating.